Portable drafting apparatus

ABSTRACT

There is herein disclosed a new and novel portable drafting apparatus comprising a board, a straightedge slidably supported on the board and consisting of an elongated blade of substantial width and having parallel longitudinal drawing instrument guiding edges, an elongated crown unit having a longitudinal tunnel for housing crossed portions of a guiding cord and mounted on the top surface of the blade and a stationary guiding cord secured at the bottom of the board and extending throughout the entire length of the crown unit and under the upper surface of the board so as to guide the straightedge in its movement about the board.

United States Patent Burgess, Jr.

[ Aug. 14, 1973 PORTABLE DRAFIINC APPARATUS [76] Inventor: William F. Burgess, Jr., 1314 f i gg g fi Penobscot Bldg" Detroit Mich Asszstant Exammer ar es PhI ips Attomey-Harness, Dickey & Pierce 48226 [22] Filed: May 6, 1971 [21] Appl. No.: 140,696 [57] ABS CT There is herein disclosed a new and novel portable drafting apparatus comprising a board, a straightedge a" slidably supported on the board and consisting of an 5 8] Fie'ld 33/80 elongated blade of substantial width and having parallel longitudinal drawing instrument guiding edges, an elem [5 6] References Cited gated crown unit having a longitudinal tunnel for housmg crossed portions of a guiding cord and mounted on UNITED STATES PATENTS the top surface of the blade and a stationary guiding 2,420,835 5/ 1947 Morrison 33/80 ord se ured at the bottom of the board and extending 2.102.008 1937 throughout the entire length of the crown unit and 19751067 191 3 under the upper surface of the board so as to guide the l,468,3l2 9/1923 Lmsner 33/80 straightedge in its movement about the board FOREIGN PATENTS OR APPLICATIONS 697,382 11 /l964 Canada 33/80 5 Chums 7 Drawing Figures l T -:;a.==r Ll I.

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PORTABLE DRAFTING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to the class of geometrical instruments and, more particularly, to new improvements in drafting apparatus.

2. Description of the Prior Art In the past, a wide variety of drafting devices have been proposed which, although working satisfactorily, have proved in the end, to be too complicated or difficult to assemble. Others have required an unwanted degree of maintenance. Still others have involved the employment of certain structural features which have proved, in practice, to be unsatisfactory and which have developed, after a period of use, irregularities in connection with the movement of the straightedge. It is recognized as of utmost importance that a straightedge must be of a construction and material which will not become distorted by reason of atmospheric conditions or constant use and which will not lose the smoothness of its edge. It is important that the means employed for insuring the accurate placement of the straightedge on the drawing surface (when moved thereover relative to previously applied lines) be such that it cannot easily get out of adjustment.

The majority of the devices presently on the market are large, cumbersome, expensive and complicated. Their sheer size and weight alone militates against the ready portability feature considered so important by students, architects and engineers, whether the use he at home, during meetings and conferences or at on'site, field inspection trips. Many employ an intricate arrangement of assembly units, usually pulleys, both on the board and either on or within the parallel straightedge member. Others utilize a cord stringing arrangement that is complicated, continually loosening, riding off the pulleys and difficult to restring. Still others are used in connection with large bulky furniture.

The present invention is adapted to overcome the ob jectionable character of the other devices through the provision of a portable drafting board which is small, economical, efficient, esthetically appealing and extremely simple to operate and maintain.

SUMMARY OF THE INVENTION It is a general object of the present invention to provide a new and improved portable drafting apparatus which is light in weight, efficient, durable and of simple construction whereby it will not only be economical to commercially manufacture, but which also will have a long operational life.

These and other objects of the present invention are accomplished by a construction which is so reduced in the number and character of its component parts as to approach the ultimate in structural simplicity to thereby epitomize economy in its manufacture, installation and maintenance.

The invention relates specifically to drafting apparatus of the type wherein a straightedge and a drafting board are coupled together through the medium of a flexible cord which is attached to the board in such a manner that the straightedge can be moved upwardly and downwardly and at the same time maintain a constant parallel relation with any lines drawn along the edge thereof and upon an underlying sheet of drawing paper.

The straightedge construction embodies a blade having a crown element mounted upon and longitudinally of the top thereof for housing crossed portions of the guiding cord.

The board may be of any suitable size and material and has an opening adjacent to each corner thereof. The cord is initially attached to the board adjacent either opening at the bottom edge of the board. It is subsequently strung in such a way that it resides under the top of the board and criss-crosses at any point within the longitudinal tunnel portion of the crown.

The various objects and advantages, and the novel details of construction of one commercially practical embodiment of the invention, will become more apparent as this description proceeds, especially when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of the drafting apparatus constructed in accordance with the preferred embodiment of the present invention;

FIG. 2 is an enlarged top plan view of the device illustrated in FIG. 1 taken within the dashed circle 2 therein;

FIG. 3 is a fragmentary side elevation view of the device illustrated in FIG. 1 looking in the direction of the arrow 3 thereof;

FIG. 4 is a cross-sectional view of the device illustrated in FIG. 1 as taken substantially along the line 4-4. thereof;

FIG. 5 is a cross-sectional view of the device illustrated in FIG. 1 as taken substantially along the line 5-5 thereof;

FIG. 6 is a cross-sectional view of the device illustrated in FIG. 1 as taken substantially along the line 6-6 thereof; and

FIG. 7 is a view of the device illustrated in FIG. I looking in the direction of the arrow 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawings, and in particular to FIG. 1, a portable drafting apparatus 10, in accordance with an exemplary embodiment of the present invention, is shown as comprising a board 12, a straightedge l4 and a single length of flexible cord 16.

The board. 12 has a smooth finish and is preferably waterproof, dent-resistant and impervious to most chemicals. It has a working or upper surface 18 and an undersurface 20. The edges are defined by a bottom edge 22, top edge 24 and a pair of side edges 26, 28. A plurality of openings 30, 32, 34 and 36 are provided at the comers of the board and are adapted to receive and retain the cord 16, to be more fully described hereinafter.

The straightedge 14 is preferably made of a clear plastic acrylic and comprises a blade 38 which is of substantial width and of sufficient length to extend substantially entirely across the width of the board 12. The longitudinal edges 40, 42 of the blade 38 are parallel with one another and form the guiding edges used for laying out lines extending transversely of a drawing sheet (not shown) which is secured upon the upper surface 18 of the board 12 and upon which the straightedge blade lies. As is best seen in FIG. 4, the blade 38 is of an equal dimension throughout its entire length and is not arched or transversely curved at any point therealong. At each longitudinal end of the blade 38, a pair of opposite and downwardly extending guiding flanges 44, 46 are integrally connected with the blade 38 and ride along in sliding engagement with the edges 26 and 28 respectively of the board 12. The flanges 44, 46 are employed for insuring the accurate placement of the straightedge 14 on the drawing surface 18 such that when the straightedge is moved thereover relative to previously applied lines, it cannot easily get out of adjustment, thus providing for the maximum possible in accuracy.

The top surface 48 of the blade 38 has formed thereon and longitudinally thereof an elongated crown unit 50. The crown 50 is preferably constructed of an opaque acrylic material and has a cross-sectional dimension which is substantially smaller than the crosssectional dimension of the blade 38. The crown S is situated approximately centrally of the blade 38 and extends longitudinally therealong terminating at a point adjacent to and short of the flanges 44, 46. The crown 50 is of an inverted U-shaped cross-sectional contour which defines a tunnel 52 which extends throughout the entire length of the crown 50.

The guide cord 16 for use in association with the apparatus may be of any suitable material. However,

prestretched, silicon-coated braided nylon has been found to be dependable, long-lasting and easy to manipulate and restring. The cord 16 has opposite ends extending through the openings and 36 and secured to the board adjacent to the openings. in stringing the apparatus 10, the cord 16 is extended from one of the openings adjacent one longitudinally spaced corner of said board, for example, opening 36 and upwardly towards the top edge 24 of the board 12 and along a first transverse edge 28. The cord 16 enters the tunnel 52 of the crown 50 passing therethrough and across the width of the board (in a right to left direction as viewed in FIG. I) to the exit end thereof and adjacent the opposite transverse edge 26. From this position the cord extends further upwardly along a line parallel to the opposite transverse edge 26 to the opening 32 and is inserted downwardly therethrough. From the opening 32, the cord is drawn along a line parallel to the adjacent top longitudinal edge 24 and below the working surface 20 of the board 12 making its entrance towards the working surface 18 of the board 12 through opening 34. Although tension is maintained throughout the entire length of the cord 16, any suitable type of fastening or retaining means may be utilized whereby the cord 16 is snugly held against the undersurface 20 of the board 12. The cord then extends towards the bottom edge 22 and along a line parallel to the first transverse edge 28 again entering the tunnel 52 of the crown 50, extending therethrough and across the board (again from right to left) exiting the tunnel at the other end thereof. The cord 16 then extends further along a line parallel to the opposite transverse edge 26 with the remaining end of the cord 16 being secured adjacent the last of the longitudinally spaced corners of said board 12 through said opening 30. It will be seen that the cord crosses itself at some point along the length of the tunnel 52. It will, of course, be appreciated that the cord may be strung from an initial starting point by using either opening 30 or opening 36. Only one cord is utilized in the stringing of the apparatus 10 and at no point does the cord extend across the working surface 18 at the top edge 24 of the board 12. This has been found to be extremely significant, particularly when working with various drafting instruments. Experience has shown that oftentimes a cord on the upper surface can obstruct the free movement of these instruments. The cord 16 may be secured adjacent the openings 30 and 36 in any suitable fashion such as by tying the cord therein or by using any suitable type of fastening or retaining means.

As best seen in FIGS. 1 and 5, a pair of non-skid members 54, 56 may be rigidly attached to the board 12 or be detachable therefrom. When attached, they are adapted to retain the board in a stationary position and to prevent any skidding or sliding thereof.

A pair of legs are detachably connected in the openings 32 and 34 and serve to retain the top edge 24 of the board 12 in an elevated position when drafting. Only one leg 60 is shown in the drawing at FIGS. 6 and 7. Leg 58 comprises a shank 62 having a plurality of threads 64 at the upper end thereof and a rubber tip 66 at the lower end thereof adapted to retain the apparatus 10 in a stationary position. A collar member 68 is held fast to the upper part of the shank 62 and has a shoulder 70 which rests snugly against the undersurface 20 of the board 12 when the leg is attached thereto. A cap screw 72 is threadably engageable with the threads 64 of the shank 62 until the lower surface thereof 74 tightens the leg sufficiently such that surface 74 is resting snugly against the upper surface 18 of the board 12. It will be contemplated that any fonn of detachable leg elevating means may be employed whereby the function of elevating the top of the board is accomplished.

From the foregoing, it will be seen that there is provided by the present invention a new and novel construction of a portable drafting board which is small in size, relatively light in weight, rugged, simple to operate and dependably accurate in use. The complete absence of a complicated array of fixtures or operating parts is apparent. The manner of stringing the apparatus 10 is likewise novel in that only one cord is utilized, it is easy to string and there is a complete absence of any obstruction at the top of the board as a result of the stringing thereof on the undersurface 20 of the board 12.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportion of the parts without departing from the scope of this invention which, generally stated, consists in the matter shown and described herein and set forth in the appended claims.

What is claimed is:

1. In portable drafting apparatus of the type wherein an instrument guiding blade extending lengthwise across a board is guided for up and down movement thereon by means of flexible cord, that improvement which comprises:

guide means on the blade comprising a longitudinal tunnel extending lengthwise of the blade for guiding cord along the length of the blade, said tunnel terminating in openings at lengthwise opposite ends thereof for reception of cord connected to the board, each of said openings being defined at least in part by edges spaced laterally relative to the direction lengthwise of the blade and projecting away from the blade; segment of cord extending downwardly from an upper comer of the board to enter the nearer lengthwise end of said tunnel via the opening thereat, then across said blade through said tunnel to exit from the opposite end of said tunnel via the opening thereat and then downwardly to the diagonally opposite corner of the board;

and a segment of cord extending downwardly from the opposite upper corner of the board to enter the nearer lengthwise end of said tunnel via the opening thereat, then along said blade through said tunnel to exit from the opposite end of said tunnel via the opening thereat and then downwardly to the diagonally opposite corner of the board;

said cord segments entering and exiting said tunnel via said openings in right angle bends which lie in planes substantially parallel to the plane of the board and which have contacting sliding engagement on and with said edges when the blade is moved up and down the board.

2. The invention as set forth in claim 1 wherein said edges are perpendicular to the plane of the blade.

3. The invention as set forth in claim 2 wherein the edges at the same end of said tunnel are aligned with each other in the direction lengthwise of the blade.

4. The invention as set forth in claim I wherein said tunnel completely encloses the portions of said cord segments running through the tunnel between the openings thereof.

5. The invention as set forth in claim I wherein said tunnel is continuous along its length. 

1. In portable drafting apparatus of the type wherein an instrument guiding blade extending lengthwise across a board is guided for up and down movement thereon by means of flexible cord, that improvement which comprises: guide means on the blade comprising a longitudinal tunnel extending lengthwise of the blade for guiding cord along the length of the blade, said tunnel terminating in openings at lengthwise opposite ends thereof for reception of cord connected to the board, each of said openings being defined at least in part by edges spaced laterally relative to the direction lengthwise of the blade and projecting away from the blade; a segment of cord extending downwardly from an upper corner of the board to enter the nearer lengthwise end of said tunnel via the opening thereat, then across said blade through said tunnel to exit from the opposite end of said tunnel via the opening thereat and then downwardly to the diagonally opposite corner of the board; and a segment of cord extending downwardly from the opposite upper corner of the board to enter the nearer lengthwise end of said tunnel via the opening thereat, then along said blade through said tunnel to exit from the opposite end of said tunnel via the opening thereat and then downwardly to the diagonally opposite corner of the board; said cord segments entering and exiting said tunnel via said openings in right angle bends which lie in planes substantially parallel to the plane of the board and which have contacting sliding engagement on and with said edges when the blade is moved up and down the board.
 2. The invention as set forth in claim 1 wherein said edges are perpendicular to the plane of the blade.
 3. The invention as set forth in claim 2 wherein the edges at the same end of said tunnel are aligned with each other in the direction lengthwise of the blade.
 4. The invention as set forth in claim 1 wherein said tunnel completely encloses the portions of said cord segments running through the tunnel between the openings thereof.
 5. The invention as set forth in claim 1 wherein said tunnel is continuous along its length. 